1. Field of the Invention
The present invention relates to a power supply system, and more particularly to a portable power supply system capable of effectively utilizing an energy resource, a fuel pack constituting the power supply system, and a device driven by a power generator and the power supply system.
2. Description of the Related Art
In all household and industrial fields, various kinds of chemical cells are used. For example, a primary cell such as an alkaline dry cell or a manganese dry cell is often used in watches, cameras, toys, and portable acoustic devices, and it has a characteristic that its quantity of production is large from the global viewpoint and it is inexpensive and readily available.
A secondary cell such as a lead storage battery, a nickel-cadmium storage battery, a nickel-hydrogen storage battery, a lithium ion battery is often used in mobile phones or personal digital assistances (PDA) which are in widespread use in recent portable devices such as a digital video camera or a digital still camera, and it has a characteristic which is superior in the economical efficiency because it can be repeatedly charged and discharged. Among secondary cells, the lead storage battery is utilized as a start-up power supply for vehicles or marine vessels or an emergency power supply in industrial facilities or medical facilities and the like.
In recent years, with the rising interest in environmental concerns or energy problems, problems concerning waste materials generated after use of chemical cells such as described above or those concerning the energy conversion efficiency have come under close scrutiny.
The primary cell has its inexpensive product price and is readily available as described above, and there are many devices which utilize this cell as a power supply. Further, basically, when the primary cell is once discharged, the battery capacity can not be recovered, namely, it can be used only once (which is a so-called disposable battery). A quantity of waste materials per year, therefore, exceeds, several millions tons. Here, there is static information mentioning that a ratio of the entire chemical cells which are collected for recycling is only approximately 20% and remaining approximately 80% is thrown away in the natural world or subjected to landfill disposal. Thus, there is fear of environmental destruction and disfigurement of the natural environment by heavy metal such as mercury or indium included in such uncollected batteries.
Verifying the above-described chemical battery in the light of the efficiency of use of an energy resource, since the primary cell is produced by utilizing the energy which is approximately 300-fold of the dischargeable energy, the efficiency of use of the energy is less than 1%. Even in case of the secondary cell which can be repeatedly charged and discharged and is superior in the economical efficiency, when the secondary cell is charged from a domestic power supply (convenience outlet) or the like, the efficiency of use of the energy drops to approximately 12% due to the efficiency of power generation in an electric power plant or the transmission loss. Therefore, it can not be said that the energy resource is necessarily efficiency utilized.
Thus, the attention is recently drawn on various kinds of new power supply systems or power generation systems (which will be generically referred to as a “power supply system” hereinafter) including a fuel battery which has less influence (burden) on the environment and is capable of realizing the extremely high energy utilization efficiency of, e.g., approximately 30 to 40%. Furthermore, for the purpose of application to a drive power supply for vehicles or a power supply system for business use, a cogeneration system for domestic use and others, or substitution for the above-described chemical cell, study and development for practical application are carried out extensively.
In the power supply system with the high energy utilization efficiency such as a fuel cell, means capable of replenishing the fuel with an easy operation when the fuel accumulated inside is run out is not established. Moreover, a fuel cell portion in the power supply system is also a durable material and, in particular, a catalyst provided inside the fuel cell is apt to be deteriorated by use of a heater or the like. Generally, such a system is life-expired earlier than a device driven by the power supply system, and a power supply system which is integral with a device must be replaced for each device or sometimes has a whale of a time being repaired.
In addition, it is impossible to avoid a problem that constituent parts (for example, a fuel tank and others) of the power supply system after the power generation fuel has been used up or its durable period has passed are discarded as waste materials, and there is the possibility that the problem of environmental destruction or disfigurement of natural environment may occur as similar to the above-described chemical cell.
In view of the above-described problems, the present invention has an advantage that environmental destruction or disfigurement by waste materials discarded after use can be suppressed in a power supply system which can be used as a substitute for a portable cell or a chemical cell, or an fuel charging portion or a power generation module which can be used as a part of the power supply system.
Additionally, in order to reduce the power supply system with the high energy utilization efficiency such as a fuel cell in size and weight and apply it as a substitute (interchangeable product) for a transportable or portable power supply, for example, the above-described chemical cell, the power supply system has the following problems.
Usually, although the fuel battery generates power by bringing alcohol fuel or hydrogen gas including a hydrogen element into contact with one of electrodes, the fuel cell itself does not control start and stop of power generation. In the power supply system including the fuel cell utilized as a power supply for a portable device in particular, therefore, even if the device is in the off mode or the standby mode and requires less power, the electric power to be supplied to the device is constantly outputted as similar to a general chemical cell and power is hence always generated, thereby deteriorating the consumption efficiency of the fuel. In order to set the volume and weight of the portable device to such values as that that the portable device can be carried or brought with the power system being accommodated therein, a quantity of fuel for power generation for the fuel cell is necessarily restricted, and it is desired that control is carried out so that the power generation fuel is further efficiently consumed and a power supply duration is prolonged.